How well is psychometric g indexed by global composites? Evidence from three popular intelligence tests.

TLDR

Global composites (e.g., IQs) in intelligence tests are interpreted as indexes of the general factor of intelligence, or psychometric g. The study aims to quantify how much of the variance in these global composites is explained by g. Hierarchical omega and omega total were calculated from large‑scale, nationally representative norming data from three popular individually administered intelligence tests for children and adolescents. Across the three batteries, 82–83 % of global composite variance was attributable to g, with group factors contributing an additional 89–91 % of total variance, showing that while global composites largely index g, group factors also play a meaningful role.

Abstract

Global composites (e.g., IQs) calculated in intelligence tests are interpreted as indexes of the general factor of intelligence, or psychometric g. It is therefore important to understand the proportion of variance in those global composites that is explained by g. In this study, we calculated this value, referred to as hierarchical omega, using large-scale, nationally representative norming sample data from 3 popular individually administered tests of intelligence for children and adolescents. We also calculated the proportion of variance explained in the global composites by g and the group factors, referred to as omega total, or composite reliability, for comparison purposes. Within each battery, g was measured equally well. Using total sample data, we found that 82%-83% of the total test score variance was explained by g. The group factors were also measured in the global composites, with both g and group factors explaining 89%-91% of the total test score variance for the total samples. Global composites are primarily indexes of g, but the group factors, as a whole, also explain a meaningful amount of variance.